Field
The present invention relates to a herbicidal suspension concentrate, more particularly to a herbicidal suspension concentrate comprising at least one sulfonamide compound and/or sulfonamide salt as the active ingredient.
Description of Related Art
When plant treatment products, in particular herbicides, are used, this may result in undesirable damage to the crop plants treated. While selective herbicides are intended to kill specific target plants and leave the desired crop relatively unharmed, a large number of selective herbicides are not one hundred percent effective in their selection, killing plant material intended for cultivation. Accordingly, the application of such herbicides on important crop plants may be substantially limited.
Occasionally, such herbicides cannot be used at all, or only at such low application rates that the desired, broad herbicidal activity against the harmful plants or unwanted plants cannot be guaranteed. In particular, herbicides of the pyridine sulfonamide class cannot be used to treat corn, rice or cereals with sufficient selectivity. Phytotoxic side-effects as a result of applying certain pyridine sulfonamides become apparent on the crop plants at various stages in the development of the plants, in particular, when the herbicides are applied post-emergence.
Accordingly, a herbicidal composition, in particular one comprising a pyridine sulfonamide as an active ingredient, capable of avoiding or reducing such phytotoxicity during the treatment of crop plants would be highly advantageous and is desirable.
Herbicidal compositions comprising pyridine sulfonamides as active ingredients are known in the art. Herbicidal active compounds from the group of the sulfonamide, such as, for example, N-[(4,6-dimethoxypyrimidin-2-yl)aminocarbonyl]-3-dimethylaminocarbonyl-2-pyridine sulfonamide, are predominantly formulated in the form of water-dispersible powders (WP) or water-dispersible granules (WG). One reason why solid formulations are preferred is that, in most cases, the pronounced sensitivity to hydrolysis of the active pyridine sulfonamide compounds. As pyridine sulfonamides are generally relatively soluble in water, the development of liquid water-based formulations is extremely difficult if the chemical stability of the sulfonamide is to be ensured. Thus, in the literature, storage-stable aqueous suspension concentrates (SC) and aqueous suspoemulsions (SE) comprising sulfonamides have been described only for a few special cases.
EP 0232067 discloses a herbicidal composition comprising a novel substituted pyridine sulfonamide compound and its salts as active ingredient and a method for preparing the same. In particular, EP 0232067 discloses that pyridine sulfonamide compounds exhibit a very high herbicidal effect and therefore may be applied to a wide range of weeds, including those which are highly resistant to other herbicides. EP 0232067 indicates that pyridine sulfonamide compounds and their salts are useful as herbicides for application on corn fields.
EP 0313317 discloses a suspended composition comprising at least one
compound selected from the pyridine sulfonamide series of compounds and the salts thereof, a vegetable oil and a surfactant, mixed together at a predetermined ratio. EP 0313317 indicates that this composition improves the herbicidal effectiveness of the pyridine sulfonamide active ingredient without causing any unwanted crop injury. As a result, a much larger variety of weeds may be controlled. Furthermore, EP 0313317 suggests that the amount of the active pyridine sulfonamide ingredient to be used may be decreased. EP 0313317 indicates that inclusion of a vegetable oil within the admixture improves the weeding effect against a broad spectra of weeds, without causing any phytotoxicity in the crops to be protected, for example corn. However, the decomposition of herbicidal pyridine sulfonamide compounds within the oil-based suspension has been found to be a problem.
EP 05540158 discloses a method for suppressing or reducing the decomposition of certain herbicidally active compounds, including pyridinesulfonamides, so as to stabilize the formulations. EP 05540158 indicates this is achieved by adding urea to the herbicidal oil-based suspension formulation.
It has now been found, however, that oil-based suspension concentrates comprising pyridine sulfonamide compounds with urea as a stabilizer, as taught in EP 05540158, spread and disperse poorly in water. This has now been found to be due to the fact that the addition of urea induces a higher hydrophilic-lipophillic balance (HLB) value to the system, increasing water solubility.
It has also now been found that pyridine sulfonamide-containing oil-based suspension concentrates in combination with other suitable stabilizers also spread and disperse poorly in water.
Accordingly, it would be advantageous to provide a herbicidal formulation of one or more pyridine sulfonamide active ingredients, which exhibits a high degree of stability of the active ingredient, while reducing the phyotoxic effects of the formulation on the plants to be protected. It would be advantageous if such formulations maintained a broad spectrum of effectiveness against unwanted plants.
Surprisingly, it has now been found that modified polyether-polysiloxane is particularly suitable for solving the aforementioned difficulties of formulating oil-based suspension concentrates of pyridine sulfonamide active ingredients. In particular, polyether-polysiloxane has been found to significantly improve the stability of the pyridine sulfonamide compounds, while overcoming the problems of spreading and dispersibility in water.